The present invention relates to fibers which are spontaneously degradable and are capable of providing textile goods having excellent properties such as bulkiness, softness and feeling, and goods made thereof, and more particularly to spontaneously degradable fibers comprising aliphatic polyesters having different thermal characteristics, and goods made thereof.
Conventional synthetic fibers made of synthetic resins are slow in rate of degradation under natural environment and generate a large amount of heat at burning and, therefore, have to be reconsidered from the viewpoint of environmental protection. For such a reason, spontaneously degradable fibers made of aliphatic polyesters are being developed, and their contributions to environmental protection have been expected. However, these spontaneously degradable aliphatic polyester fibers are not satisfactory in bulkiness, softness, feeling and so on, and an improvement thereof has been desired.
Conventionally it is known that goods such as knitted and woven fabrics having excellent bulkiness and softness are obtained if fibers having a different shrinkability are combined in usual inter-fiber composites (blends of fibers). However, as to aliphatic polyester fibers having a spontaneous degradability, a manner of controlling the shrinkability has been scarcely known so far and, of course, it is not known at all to conjugate fibers having a different shrinkability and to improve the quality of knitted fabrics and woven fabrics by using it.
Also, in order to obtain a fiber having a high softness and various functions based on a special shape of section and a large surface area, it has been conventionally practiced to divide a dividable conjugated fiber. By this method, there have been developed and widely used knitted and woven fabrics, non-woven fabric, artificial leather, artificial suede, high performance wiping cloth, high performance filter and so on. However, in the field of degradable fibers in natural environment, no dividable conjugated fiber has been proposed. The reason is that combination of spinning materials (polymers) suitable for division and how to divide have not yet been known.
A self-adhesive (melt-adhesive) fiber that a part of a fiber melts by heating to adhere fibers to each other, has been widely used in the field of synthetic fibers. Melt-adhesive fibers using an aliphatic polyester are proposed in Japanese Patent Publications Kokai No. 6-207320 and Kokai No. 6-207324. However, in working examples thereof, a conjugated fiber composed of a sheath (adhesive component) of a polyethylene succinate having a melting point of 102xc2x0 C. and a core (strength-retaining component) of a polybutylene succinate having a melting point of 118xc2x0 C. is only disclosed, and the adhesive strength thereof is not so strong. The reason is that the difference in melting point between both components is as small as only 16xc2x0 C. and the strength-retaining component is softened and deteriorated by heating for adhesion. Also, the optimum temperature for adhesion treatment of this fiber is limited within a very narrow range, so it is very difficult to exhibit desired adhesive force and strength. It is also very difficult to alter the adhesive strength in a wide range according to the purposes, so the uses are limited. In general, a low-melting component has been used for the adhesive component of melt-adhesive fibers. However, if a low-melting aliphatic polyester having a melting point of not more than 120xc2x0 C. is used, the glass transition temperature is lower than ordinary temperature, so the solidifying rate is slow and, therefore, there arise many problems in practical use such that fibers are easy to stick to each other at the time of melt-spinning, so not only production at a high speed is difficult, but also the heat resistance in use is low.
An object of the present invention is to provide a spontaneously degradable fiber excellent in bulkiness, softness, feeling and stretchability, and textile goods prepared therefrom.
A further object of the present invention is to provide a spontaneously degradable fiber having a self-crimpability.
A still further object of the present invention is to provide a self-crimpable fiber which is spontaneously degradable, which reveals an excellent crimp by heating or the like so as to be able to provide goods excellent in softness, bulkiness and stretchability and, moreover, which can be easily prepared in high efficiency.
Another object of the present invention is to provide a conjugated fiber which is spontaneously degradable, which has an improved dividability and which can provide fibers and fiber structures having an excellent softness and a large surface area.
A still another object of the present invention is to provide a self-adhesive fiber which is spontaneously degradable, which exhibits an excellent adhesion property by heat treatment for adhesion and, moreover, has an excellent strength because of less deterioration of a strength-retaining component, which can be prepared by melt-spinning at a high velocity, and which can easily produce adhesive fiber structures having an excellent heat resistance, and to provide a fiber structure using it.
A further object of the present invention is to provide a self-adhesive fiber which is spontaneously degradable and which can be subjected to adhesion treatment within a wide temperature range and can widely alter the adhesive strength according to the purposes.
A still further object of the present invention is to provide a fibrous bulk material which is spontaneously degradable and is composed of a mixture of a plurality of fibers which show a different shrinkability by heating or the like, thus producing a difference in length between the fibers by heating, and accordingly which can provide goods excellent in bulkiness, softness and feeling.
As a result of repeating intensive study, the present inventors have found that the above objects can be achieved by combining spontaneously degradable aliphatic polyesters having different thermal properties such as heat absorption amount in melting (the heat of fusion), melting point and the like, thus having accomplished the present invention.
Thus, the present invention provides a fiber comprising (A) a fiber component comprising an aliphatic polyester having a melting point of at least 100xc2x0 C. and a heat of fusion of at least 30 J/g and (B) a fiber component comprising an aliphatic polyester having a melting point of at least 100xc2x0 C. and a heat of fusion lower than that of said polyester (A) by at least 5 J/g. In the present invention, the fiber comprising the fiber components (A) and (B) may be in the form of a conjugated fiber wherein the components (A) and (B) are conjugated in a single filament, or in the form of a composite yarn wherein fibers of respective components are blended. Since this fiber comprises (A) high crystalline component having a high heat of fusion and (B) low crystalline component having a low heat of fusion, it has excellent bulkiness, softness and feeling, based on a difference in heat shrinkability and, in particular, the fiber formed in the form of a conjugated fiber exhibits an excellent self-crimpability and provides a fiber excellent in stretchability.
Further, the present invention provides a fiber comprising (A) a fiber component comprising a crystalline aliphatic polyester having a melting point of at least 140xc2x0 C. and (B) a fiber component comprising a combination of (H) a component comprising a crystalline aliphatic polyester having a melting point of at least 110xc2x0 C. and (S) a component comprising a crystalline aliphatic polyester having a melting point which is not more than 120xc2x0 C. and is lower than that of said polyester (A) by at least 10xc2x0 C. or a non-crystalline aliphatic polyester having a glass transition temperature of at most 30xc2x0 C. The aliphatic polyester components (H) and (S) in the fiber component (B) of this fiber may be in the form of a block copolymer of the both components or a mixture of the both components. This fiber has excellent bulkiness, softness and feeling, since it comprises the fiber component (A) comprising a high-melting polymer having a low heat shrinkability and the fiber component (B) containing a low-melting or non-crystalline component (S) which greatly contributes to heat shrinkability. In particular, a conjugated fiber wherein (A) a crystalline aliphatic polyester having a melting point of at least 140xc2x0 C. and a heat of fusion of at least 20 J/g is eccentrically conjugated in a single filament with (B) a block copolymer and/or mixture of at least two crystalline aliphatic polyesters (H) and (S), the difference in melting point between them being at least 20xc2x0 C., which contains 90 to 10% by weight of the high-melting component (H) having a melting point of at least 130xc2x0 C. and a heat of fusion of at least 3 J/g and 10 to 90% by weight of the low-melting component (S) having a melting point of 40 to 120xc2x0 C. and a heat of fusion of at least 3 J/g, has an excellent self-crimpability. Also, the conjugated fiber wherein the component (B) is conjugated so as to form at least a part of the surface of the fiber, has an excellent self-adhesive property. Further, a spontaneously degradable conjugated fiber which is easily degradable is obtained by conjugating (A) a crystalline aliphatic polyester having a melting point of at least 140xc2x0 C. with (B) a block copolymer and/or mixture of a crystalline aliphatic polyester component (H) having a melting point of at least 140xc2x0 C. and an aliphatic polyester component (S) having a melting point of at most 120xc2x0 C. and a glass transition temperature of at most 30xc2x0 C. in a single filament into a dividable shape. Also, in case that the fiber component (B) is a block copolymer, the crystalline aliphatic polyester component (H) having a melting point of at least 110xc2x0 C. may contain urethane bonds.
Also, the present invention provides a conjugated fiber wherein (A) a crystalline aliphatic polyester having a melting point of at least 140xc2x0 C. is conjugated in a single filament with (B) a composition comprising an aliphatic polyester and 1 to 50% by weight of at least one compound selected from the group consisting of a polyether having a C2 to C4 alkylene group, its derivatives, an organic compound having a sulfo group, an organic compound having sulfate group, an organic compound having carboxyl group, an organic compound having phosphate group and an organic compound having amino group and/or amido group, and in the cross section thereof the composition (B) divides the polymer (A) into at least two portions. This conjugated fiber is subject to hydrolysis and can be easily divided, since the component (B) contains a specific hydrophilic compound.
Further, the present invention provides a yarn, a staple, a cotton, a tow, a web, a knitted fabric, a woven fabric, a non-woven fabric and a fibrous bulk material analogous thereto wherein (X) a core-sheath conjugated fiber having a sheath of (A) a crystalline aliphatic polyester having a melting point of at least 140xc2x0 C. and a core of (C) a polymer containing at least 10% by weight of (B) an aliphatic polyester having a melting point lower than that of the polymer (A) by at least 20xc2x0 C. is blended with (Y) a spontaneously degradable fiber other than the fiber (X).